Two position mechanism

ABSTRACT

The mechanism includes one member which may occupy one of two fixed positions and can be caused to change over from one position to the other at will. In order to accomplish rapid change over with minimum energy input and minimum impact, an elastic suspension of this member is provided and so arranged that the changeover process is substantially a half cycle of oscillation in which the moving member starts and ends with no or little speed of motion. The moving member is captured in the vicinity of, and held at the fixed positions, against the force exerted by the elastic suspension by mechanisms exerting short range forces upon it.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to mechanisms and specifically those mechanismswhich have only two defined rest positions, but do not exercise rigidcontrol over the motion of the member which is moved from one restposition to the other. For convenience, such mechanisms will hereafterbe referred to as binary mechanisms.

2. Discussion of Related Art

Some examples of binary mechanisms are: electric relays, solenoidactuators, manually operated electric switches, and thermally actuatedelectric switches utilising differential expansion of metals. In eachcase, there has to be provided a means for applying a force or forces tothe said moving member, hereafter referred to as the oscillator, and forremoving this force or forces. This force or forces may be generatedmechanically or electromagnetically, by the action of fluid pressure orvacuum, manually or inertially.

The great variety of modes of operation of binary mechanisms is alsoreflected in the great diversity of their application and for thisreason, a functional rather than operational definition is foundconvenient.

It is a feature of binary mechanisms that, as the motion of theoscillator is not under rigid control, there is a degree of impact asthe oscillator changes over from one rest position to the other. Thecombination of short change-over time and substantial oscillator massleads to excessive impacts and an excessive requirement of energy forgenerating the said force or forces.

SUMMARY OF THE INVENTION

It is an object of this invention to minimize the severity of the saidimpacts and also to minimize the said energy requirement.

In the present invention, the oscillator is suspended from a spring orspring system so arranged that, during the early part of thechange-over, spring forces act to accelerate the oscillator, whileduring the latter part of the change-over, they act to decelerate theoscillator. By this means, the greater part of the energy associatedwith the change-over is released and stored again in the spring orspring system, and only energy losses incurred during the change-overneed to be supplied.

To hold the oscillator at either of the said fixed positions, againstthe pull of the spring or spring system, capture/release mechanisms areprovided at each of the fixed positions, able to exert short rangeforces exceeding the spring forces; by means of which the oscillator,when approaching the fixed positions, is attracted to and held at thefixed positions. To release the oscillator from the fixed positions atany time, the short range force is temporarily suppressed, whereupon thespring force sets the oscillator into motion, causing it to execute ahalf cycle of oscillation which brings it into the vicinity of theopposite fixed position, where it is again captured and held untilreleased in the aforesaid manner.

In various embodiments of this invention, the said spring or springsystems may comprise elastic solids or suitablcontained fluids. The saidcapture/release mechanisms may exert mechanical forces; forces due topressure or vacuum; or forces due to magnetic fields. The best method ofperforming this invention known to me embodies springs of suitablyformed elastic solids, and capture/release mechanisms exerting forcesdue to permanent magnets which are neutralised and amplified by means ofsuitable electric current carrying coils to effect release and capturerespectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects of the present invention will become morereadily apparent as the invention becomes more fully understood from thedetailed description below, reference being made to the accompanyingdrawings in which like reference numerals represent like partsthroughout and in which:

FIG. 1 is an elevational sectional view showing a first embodiment of atwo position mechanism according to the present invention;

FIG. 2 is an elevational sectional view showing an embodiment of thepresent invention including a provision for imparting additional energyto the mechanism and an adjustment for the neutral position of themechanism;

FIG. 3 is an elevational sectional view showing an embodiment of theinvention including fluid springs;

FIG. 4 is an elevational sectional view showing an embodiment of theinvention using pressure actuated capture/release mechanisms, and

FIG. 5 is an elevational sectional view showing an arrangement ofmechanical capture/release mechanisms.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a particular embodiment of the invention in which abinary mechanism is used to switch a poppet type valve between the fullon and full off positions, which correspond to the rest positions of theoscillator which, in the present instance includes the valve. In FIG. 1,the valve is shown in the half-open positon at which the oscillatorexhibits its greatest speed of motion.

With reference to FIG. 1, two helical coil springs, 1 and 2, containedbetween valve body 13, and upper mounting plate 14, act on theferromagnetic capture disk 11, tending to hold it in the position shown,so that a force is required to displace capture disk 11 and with itvalve 12 either up or down.

Also attached to mounting plate 14 is the upper capture releasemechanism comprising permanent magnet ring 3 preferably ofnon-conductive composition, and magnetised radially; ferromagnetic polepieces 5 and 6, and power coil 9.

In like fashion mounting plate 15 supports the lower capture/releasemechanism comprisng permanent magnet ring 4; ferromagnetic pole pieces 7and 8; and power coil 10; the mounting plates 14 and 15 being supportedby a multiplicity of bolts 16 with tubular spacers 17 engaging with andheld firmly upon the upper surface of valve body 13.

If, by means of an external agency, valve 12 is now pushed upwards, itwill encounter an increasing spring force due to springs 1 and 2 as thecapture disk 11 approaches pole pieces 5 and 6. However, in the vicinityof the pole pieces 5 and 6, the magnetic force will equal the springforce, and as it is acting in the opposite direction, balance it.Further upward displacement will cause capture disk 11 to snap onto thepole pieces 5 and 6 and be held there indefinitely.

By means of power coil 9, the effect of permanent magnet 3 may beamplified with electric current of suitable polarity, and by this meansthe said balance of forces may be achieved at a greater distance frompole pieces 5 and 6. Conversely, by reversing the polarity of theelectric current in power coil 9, the effect of permanent magnet 3 maybe partially or wholly cancelled, thereby effecting the release ofcapture disk 11 from the upper capture/release mechanism.

At the instance that capture disk 11 is released by the uppercapture/release mechanism, the oscillator, comprising in this instancecapture disk 11 and valve 12, proceeds to execute a half cycle ofoscillation beginning from rest at the upper pole pieces 5 and 6 andending again at rest in the vicinity of the lower pole pieces 7 and 8,except that the magnetic force due to pole pieces 7 and 8, imposes anadditional displacement causing capture disk 11 to snap against thelower pole pieces 7 and 8 and remain there.

Power coils 9 and 10 may be connected in series or parallel, to form asingle electric circuit, but in opposed sense, so that the effect of theone magnet is amplified when that of the other is diminished. When thisis done, current effecting release from one capture/release mechanismneeds only to be sustained until the oscillator is re-captured by theopposite capture/release mechanism to amplify the action of thecapturing magnet force during re-capture.

The neutral position of the said oscillator is that where there is nonet spring force and lies between the fixed positions. Where theoscillator encounters a greater resistance in one direction of motionthan the other, the fixed positions ae unequally disposed about theneutral position. Now the said oscillator, after encountering thegreater resistance, is captured at the fixed position closer to theneutral point, and after encountering the lesser resistance, theoscillator is captured at the fixed position further from the neutralpoint.

So far the capture/release mechanisms have been presented as the solesource of external energy to the oscillator. However, instances areenvisaged, where it is desirable to supply a portion of the externalenergy by means other than the capture/release mechanisms, and atdifferent points in the motion of the oscillator, to best compensate forthe resistance to the motion of the oscillator in special cases.

The disadvantages of binary mechanisms in the present state of the art,to which this invention is directed, become most significant foroscillators of substantial mass and short change-over times.

It is envisaged that the present invention could be used to greatadvantage in high voltage, high power switching equipment; in internalcombustion engines where total control of valve timing permitssubstantial improvement in part load efficiency, as well as increasedmaximum power; in gas and vapour expanders with variable inlet valvecut-off, for which the present invention is ideally suited; inmechanical indexing where random timing is necessary; as well as many ofthe applications for which solenoid type actuators are presently used.

FIG. 2 shows a provision for imparting additional energy to theoscillator and for adjusting the neutral position of the oscillator(where the nett spring force is zero). Spacers 16 and 17 allow theneutral position of the oscillator to be determined. An electromagneticactuator comprising ferromagnetic core 20, winding 10 and ferromagneticarmature 18 is provided for imparting additional energy to theoscillator. The winding 19 is normally not energized and the armature 18therefore rests against the stop 21. If the oscillator is held by theupper capture/release mechanism, additional energy may be imparted byenergizing coil 19 concurrently with or slightly before coil 9 isenergized. This causes armature 18 to be pulled against core 20 therebycompressing spring 1 further. When the oscillator is subsequentlyreleased, this additional energy is imparted to it. After capture of theoscillator by the lower capture/release mechanism, coil 19 is thende-energized. By suitable adjustment of the neutral position, theadditional energy may be expended by the oscillator in either thedownward or upward motion or both.

FIG. 3 shows a configuration using fluid springs. Piston 22 is part ofthe oscillator and moves in the housing 23 containing two isolatedchambers of compressible fluid 24. Seals 25 prevent leakage ofcompressed fluid.

FIG. 4 shows a configuration using pressure actuated capture/releasemechanisms. It comprises a chamber 26 and disk 29 supported on waistedshaft 30. The chamber is pressurized through inlet 31 and vented toatmosphere (or connected to a vacuum) through valves 33 and 34 which arenormally open. The disk has a clearance with the chamber wall but whenit approaches compressible seal 27 or 35, a pressure differentialdevelops holding the disk against the seal. To release the disk from,for example seal 27, valve 33 is closed and valve 28 is opened to thehigh pressure supply and pressure across the disk is equalized. As thedisk moves away, the enlarged portion of shaft 30 seals off groove 35,preventing loss of fluid when valve 28 is closed and 33 is opened again.

FIG. 5 shows an arrangment of mechanical capture/release mechanisms.Levers 37 and 38 are pivoted on brackets 41 and 42 while springs 39 and40 keep the levers in contact with the oscillator stem 46. Theoscillator is captured in the upper position by lever 38 as soon as itcomes to rest and begins downward motion by frictional "jamming". Torelease the oscillator, an impulse 44 is imparted to the free end oflever 38, which lifts the lever out of contact with stem 46 until it isagain captured by lever 37 in the lower position. At the same time thatimpulse 44 is applied to lever 38 another impulse 45 is applied to theoscillator stem to make up for energy losses during one cycle ofoperation. The oscillator is released from the lower position by impulse43.

The claims defining the invention are claimed as follows:
 1. A mechanismcomprising:a member which is movable between two fixed positions;biasing means for applying oppositely directed biasing forces on saidmember to normally hold said member between said two positions such thatsaid biasing means accelerates said member during a first portion oftravel between said two positions and decelerates said member during asecond portion of said travel, said biasing means comprising a springsystem connected to said member and dimensioned such that, when saidmember is released from one of said fixed positions, said spring systemaccelerates said member during said first portion of travel anddecelerates said member during said second portion causing said memberto enter a location in the vicinity of the other fixed position,capture/release means for capturing said member in the vicinity of oneof said two positons and releasing said member at will to permit saidmember to move toward the other of said two positions under theinfluence of said biasing means, said capture/release means comprising:force applying means for applying a force to said member to overcomesaid biasing means and cause said member to move from said location inthe vicinity of said other fixed position into said other fixed positionwhereby each time said member is released from one of said positions,said member travels under the influence of said biasing means and saidforce applying means through substantially a half cycle of operation tothe other of said fixed positions and said biasing means aids in themovement of said member during a first portion of said half cycle andretards the movement of said member during a second portion of said halfcycle in order to accomplish a rapid changeover with minimum impact,wherein said capture/release means comprises two capture/releasemechanisms positioned to capture said movable member in said twopositions, respectively, wherein said movable member includes aferromagnetic armature, and each of said capture/release mechanismscomprises a permanent magnet, and an electrical coil positioned toaffect the magnet field produced by said permanent magnet, wherein thecoils of each of the two capture/release mechanisms may be energizedoppositely so that the effect of one of said permanent magnets isamplified while the effect of the other permanent magnet is neutralized.